Well, I can speak for Diaspora as it's founders are rooted in activism and ideals for the social network are privacy oriented. Diaspora is also decentralized and it's something you can run on your own. The open source nature also creates transparencies. If you combine it with hardware like Freedom Box it becomes a different kind of monster.

You're very right, that GMX and DuckDuckGo can both change their philosophies at any point. What we really need is to make encryption something very easy to use and widely implemented. There are some services like Riseup.net that offer this already, but they're in their infant stages and not meant for a wide user base.